The overall objective is to determine if the biliary micelle is formed within the liver cell prior to secretion into bile and in particular, to determine if the hepatocyte endoplasmic reticulum and Golgi apparatus are involved in biliary lipid secretion. The specific aims are: 1) to search for biliary bile acid-lecithin-cholesterol micelles in microsomal and Golgi fractions of rat liver, and other subcellular organelles. 2) to analyze the structural and compositional subcellular changes, which occur in hepatocytes, during enhanced or reduced biliary lipid secretion, particularly in microsomal and Golgi fraction. 3) to define the relationship between the hepatic secretion of lipoproteins into plasma and lipids into bile, in the rat. These aims will be accomplished by studying both enhanced and reduced, bile lipid output and hepatic lipoprotein secretion in the rat, using a combined functional and morphological approach. Cell fractionation will be the major experimental technique, combined with morphological and biochemical analysis of subfractions (including protein, lipid and marker enzyme assays). Intracellular micelles, isolated by column chromatography, will be characterized by lipid analysis while the lipid content of microsomes, Golgi apparatus and serum will be analyzed for lipoprotein classes. The hepatic ultrastructure in experimental and control rats will also be examined by thin-section electron microscopy and morphometry. Ultimately a complete examination is planned, of the cellular basis of bile lipid secretion and its relationship to hepatic lipoprotein metabolism. This information will be invaluable for understanding human cholesterol cholelithiasis and lipid metabolism - particularly with respect to cardiovascular disease and the lipid abnormalities associated with biliary obstruction and other liver disorders. After 2 years of full-time basic research in the Liver Study Unit the candidate was appointed Assistant Professor of Medicine (October 1981). Medical training in Britain (1969-1979) included clinical research on biliary lipid secretion. The Liver Unit is an ideal place for this project. The Director is well experienced in research, the equipment and technical expertise are excellent and interaction with basic science departments such as Cell Biology and Physiology is readily available.